Timing requirements for driving HobbyCNC Pro 4

[Peter Gregson]

Hello,

I am planning to drive the HobbyCNC Pro 4 board with a BeagleBone Black running Machinekit. However, I need to know what the timings have to be. Specifically, I need:
1. the minimum step duration,
2. the step period, and
3. the setup and hold times for the direction signals with respect to both the leading and trailing edges of the step signal.

I would like to know any other timings that I need as well.

If there are any “gotcha’s”, please inform me of them. Presumably, the steppers themselves impose timing limits. These I can determine through experimentation, I believe. Please correct me if I am wrong; I would hate to destroy the HobbyCNC Pro 4 that has served me well for years just because I want to upgrade my milling machine.

Best regards,
Peter

[Richard Schmidt]

You could consult the data sheet for the SLA7078M driver chips. The document should provide all of the information you want. Search for Allegro Microsystems and SanKen Devices. Hope this helps get you what you need.
Cheers,
Rich Schmidt

[BrianV]

Thanks Richard, yes, this is the right answer. Step and direction signals route directly to the chip from the 25pin D connector.

https://www.semicon.sanken-ele.co.jp/sk_content/sla7077mprt_ds_en.pdf

As long as you keep the voltage to those pins at 5V (I’m pretty sure they work with 3.3V too).

Although it’s for Arduino, you can probably get some info from here: https://hobbycnc.com/hobbycnc-and-arduino/

BrianV

[Peter Gregson]

Thanks Brian. Your response is most helpful. The Arduino site has lots of useful timing information. Also, from a preliminary review of thee Sanken SLA7078MPRT data sheet, it appears that you are right and that the inputs can be 3.3 volts.

Is there any chance of getting a schematic for the HobbyCNC Pro 4? I’m an electrical and electronic engineer and I would like to better understand the design of the board.

Best regards,

Peter

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